温控近红外光谱用于葡萄糖的高灵敏检测

温控近红外光谱在混合体系定量分析以及分子间相互作用分析中已得到应用.本工作利用互因子分析方法(MFA)探索了温控近红外光谱技术测定血清样品中低浓度葡萄糖含量的可行性.测量了不同温度下葡萄糖含量分别为1.0～15.0 mmol/L和0.0～1.0 mmol/L的两组血清溶液的近红外光谱,并利用MFA进行了定量计算.结果表明,利用该方法可以实现样品中微量葡萄糖的准确定量,MFA提取的标准信号(SS)的相对强度和葡萄糖浓度之间的线性相关系数R分别为0.9923和0.9895,预测均方根误差(RMSEP)分别为0.35和0.07 mmol/L.     

ICA方法与NIR技术用于药片中活性成分含量的测定

用独立分量分析(ICA)方法提取药片近红外光谱数据矩阵的独立成分和相应的混合矩阵, 再用BP神经网络对混合矩阵和药片中活性成分的浓度矩阵进行建模, 提出了新的药片活性成分含量测定的基于独立分量分析-神经网络回归(ICA-NNR)的近红外光谱分析方法. 通过分析独立分量数和网络中间隐层的神经元数对模型性能的影响, 分别建立三类药片定量分析的最优模型. 该方法用于实测的三类药片中活性成分含量的测定, 测试样品集的化学检测值与近红外预测值的相关系数分别达到0.962, 0.980及0.979. 结果表明, 基于ICA-NNR的近红外光谱分析方法对制药业的药片进行定量分析是可行的.     

近红外光谱法快速检测烟草中部分香气物的应用研究

应用傅立叶变换近红外漫反射光谱仪,从500个样品中按高、中、低含量挑选出具代表性的150～172个烟草样品建立了近红外光谱与烟草中的苹果酸、柠檬酸和石油醚提取物成分含量间的数学模型,用建立的模型对36个样品进行预测,结果表明,各成分近红外预测值与实测值之间的平均偏差:苹果酸为0.090,柠檬酸为0.040,石油醚提取物为0.124;且近红外预测值与化学法不存在显著性差异,近红外光谱分析技术可初步用于烟草部分香气成分的快速定量分析.     

离子交换法富集、分离和测定污水中微量胺乙基硫代磷酸酯

0,0-二烷基 S-(2-二烷基胺乙基)硫代磷酸酯(DEPT)的分析方法很多。但测定污水(或复杂成分)样品中的微量 DEPT 时,因含量低微,干扰众多,直接测定是困难的。据文献报道,利用离子交换树脂富集和分离水样中微量无机离子或有机离子,主要是利用离子交换特性进行富集和层析分离,不但需要检测手续,而且试样被洗脱液稀释。本文介绍一种利用离子交换树脂的离子交换性,并与以树脂为载体的柱上化学反应相结合的方法,用于富集、分离和测定污水(或复杂成分)样品中的 DEPT,获得良好效果。     

雪菊中木犀草苷的富集及近红外光谱分析方法

采用温和的方法制备了苯硼酸吸附剂,将其用于雪菊中微量木犀草苷的富集,并以此为基础建立了快速、选择性地测定雪菊中木犀草苷含量的近红外光谱分析方法。富集了木犀草苷的吸附剂无需脱附,即可用近红外漫反射光谱直接检测,通过偏最小二乘回归法建立了定量分析木犀草苷的校正模型,并成功实现了木犀草苷含量的测定。采用此苯硼酸吸附剂0.2 g,常温振荡吸附20 min后,吸附效率可达85.5%。结果表明,经连续小波变换处理近红外光谱分析数据,木犀草苷预测模型的预测浓度和参考浓度之间的相关系数为0.9765,且木犀草苷在0.15～19.5 mg/L浓度范围内具有较好的预测结果,预测回收率为84.7%～113.2%。本研究建立了苯硼酸吸附剂吸附预富集方法,与近红外漫反射光谱结合,实现了雪菊溶液中微量木犀草苷的选择性测定,为近红外光谱与吸附富集分析药食用植物中的其它有效成分的研究提供了参考。     

用傅里叶变换近红外光谱和偏最小二乘法测定蔬菜中硝酸盐含量

1　引　　言近红外光谱分析技术 (NIRS)是利用物质在近红外光谱区的光学特性快速测定某种物质中的一种或多种化学成分含量的新技术。它以分析速度快、样品准备简单、从单个光谱可进行多种分析、不破坏样品及没有化学污染等优点 ,已广泛用于众多领域的定量分析及过程控制。被称为是一种绿色、快速、高效、适合在线分析的测试手段。蔬菜是极易富集硝酸盐的作物 ,人体摄入的硝酸盐有 81.2 %来自蔬菜 ,进入人体的硝酸盐可转化为亚硝酸盐 ,使人体缺氧中毒产生高铁血红蛋白症。硝酸盐还是一种潜在的致癌物质 ,因此 ,快速的硝酸盐检测方法对于监…     

短波近红外光谱技术对葡萄酒中总糖含量快速测定的研究

采用短波近红外光谱技术结合偏最小二乘法(PLS),建立了葡萄酒中总糖含量的定量分析数学模型,讨论了光谱预处理方法和主成分数对PLS模型预报精度的影响.应用所建模型对预测集样本中总糖含量进行预报,结果令人满意.该方法方便快捷,并且具有较高的预报精度,可以用于葡萄酒中总糖含量的快速测定.     

近红外光谱法对头孢氨苄粉末药品的非破坏定量分析

采用近红外漫反射光谱法对头孢氨苄粉末药品中主要成分头孢氨苄进行快速、无损定量分析.采用偏最小二乘法建立近红外光谱信息与待测组分含量间的最佳数学校正模型.对3种光谱(SNV光谱、一阶导数、二阶导光谱)的预测结果进行了比较,讨论了光谱的预处理方法和主成分数对偏最小二乘法定量预测能力的影响,并对预测集样品进行预测.     

主成分分析-支持向量回归建模方法及应用研究

将主成分分析(PCA)用于近红外光谱的特征提取,并与支持向量回归(SVR)相结合,实现了主成分分析-支持向量回归(PCA-SVR)用于近红外光谱定量分析的建模方法。与单纯的SVR方法相比,不仅提高了运算速度,而且提高了模型的预测准确度。将PCA-SVR方法用于烟草样品中总糖和总挥发碱含量的测定,所得结果的预测均方根误差分别为1.323和0.0477;回收率分别为91.8%~112.6%和88.9%~120.2%。     

银镜增强的近红外漫反射光谱法测定血清尿素

针对近红外漫反射光谱(NIRDRS)技术灵敏度低或检出限高的缺点,采用银镜作为吸附基底以改善其灵敏度.银镜的强反射能力不仅能够降低光谱的背景干扰,还能增强光谱的响应信号.研究了NIRDRS技术结合银镜基质用于快速定量分析血清尿素含量的可行性.直接采集富集了血清的银镜基质的NIRDRS光谱,结合光谱预处理和变量选择方法,采用偏最小二乘回归建立了定量校正模型并进行快速预测.结果表明,采用银镜基质结合NIRDRS技术可以准确地测定含量为2.8~26.1 mmol/L的血清尿素,预测值与参考值的相关系数(R2p)为0.9823,样品回收率为86.0%~117.0%,且预测得到的最大误差值低至1.45 mmol/L.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.